In the past, adaptive primary transforms (AMT: Adaptive Multiple Core Transforms) have been disclosed in which, for each of a primary transform PTor in a horizontal direction (also called primary horizontal transform) and a primary transform PTver in a vertical direction (also called primary vertical transform), a primary transform is adaptively selected from a plurality of different orthogonal transforms (for example, refer to NPL 1).
It is to be noted that also it is disclosed in NPL 1 that, for each of a horizontal direction (x direction) and a vertical direction (y direction), a transform set TransformSet including orthogonal transforms that become candidates for a primary transform is (uniquely) determined (selected) on the basis of a correspondence table (intra prediction mode information) between mode information and transform sets. Also it is disclosed that a definition of a transform set is determined on the basis of a transform block size and mode information (for example, refer to NPL 2).